A styrene copolymer comprising resin matrix and elastomer or rubber is exemplified by acrylate-styrene-acrylonitrile (ASA), olefin-styrene-acrylonitrile (OSA), acrylonitrile-ethylene propylene diene rubber (EPDM)-styrene (AES) and acrylonitrile-butadiene-styrene (ABS). These resins have different characteristics according to their elastomer components. In particular, ASA resin has excellent impact strength, processibility and weatherability, while ABS resin has excellent low-temperature impact resistance and processibility.
Thermoplastic resins such as ABS and ASA resins are in increasing demand in a variety of fields including household supplies, automobile interior materials, office equipments, and construction materials. Most products produced by using such thermoplastic resin compositions has high gloss and the extruded products prepared from ABS, AES and ASA resins have high surface gloss (75° gloss: 90) or medium surface gloss (75° gloss: 60).
With recent demand for emotional quality of a product according to the rising sensitivity to beauty of a customer, a low surface gloss resin is also in increasing demand. Besides, with the rising concern about environment conservation, it has been a new trend to use a low gloss resin directly for the production with eliminating the processes of low gloss painting and covering pad. Particularly, the use of a low surface gloss resin composition for the production of structure sidings, computer housings and keyboards, electric appliances and auto-parts has been significantly increasing. Therefore, ABS, AES, and ASA resins, preferably ASA resin most of all, with reduced surface gloss but having as excellent properties as the conventional ASA resin must be preferred in the field of construction, especially for the production of exterior articles for structures including sidings.
To produce a low surface gloss resin, it is the most common method to regulate smoothness of the resin surface to be larger than visible spectral region so as to scatter away the incident rays, resulting in glossless effect.
Embossing and low gloss coating on the surface of a molded product have been conventionally tried. However, these methods require an additional process with increasing the production cost, and produce a molded product with less glossless effect on its surface and with poor processibility.
Another conventional method is to add a specific rubber or elastomer component to improve the quality. Precisely, this method is exemplified by the following three methods. First is the method to improve ABS resin by using large caliber rubber particles of at least 2□ in mean diameter produced by bulk polymerization. However, the resin prepared by this method has insufficient low gloss effect in addition to poor impact strength and heat resistance. Second is the method to add a glossless filler of at least 5□ in mean diameter to a resin. However, the resin prepared by this method also has problems of insufficient low gloss effect and very poor impact strength, even if it has excellent formability. Third is the method to produce ABS resin by grafting ABS polymer prepared by emulsion polymerization with such a modifier as ethylene-unsaturated carboxylic acid, which has been widely used these days, because the resin prepared by this method has excellent impact strength and general physical properties and low gloss effect. However, this resin also has limitation because when it is applied to weatherable resin (ASA), heat-resistance and weatherability are reduced.
U.S. Pat. No. 5,081,193 describes a matting agent for thermoplastic resin which comprises the graft copolymer containing low-cis polybutadiene as a rubber component. U.S. Pat. No. 5,237,004 describes a method for reducing surface gloss by adding 2-15□ sized polymer particles to the thermoplastic polymer composition having core/shell structure. U.S. Pat. No. 5,475,053 describes a molding composition having glossless surface which comprises an impact strength improved thermoplastic resin such as ABS or ASA and a matting agent. U.S. Pat. No. 4,652,614 describes a molding material having glossless surface prepared by using neutral and acidic graft polymers as a substrate. U.S. Pat. No. 4,169,869 describes ABS compound having low surface gloss or glossless finish. U.S. Pat. No. 4,668,767 describes a graft polymer having glossless surface which comprises 20-0.1 weight part of heterocyclic nitrogen substrate in micro-particular rubber containing rubber by 5-80 weight % in total and having mean diameter of 0.05-20.0□ and glass transition temperature of up to 10° C.; 40-99.8 weight part of aromatic vinyl monomer; 20-0.1 weight part of mono- or di-acid containing a polymerizable double bond; and 0-40 weight part of acrylonitrile.
However, all the conventional methods are limited in satisfying the required qualities and properties such as weatherability, impact resistance, reduced surface gloss, surface quality, production costs and processibility and have at least one of disadvantages.